Screw Compressor Having Slide Valve With Flexible Volume Ratio

ABSTRACT

A screw compressor includes a casing, a screw, an air entry, an air outlet, a slide valve with a flexible volume ratio, and first and second air cylinders. The slide valve is disposed between the first and second air cylinders and includes a slide valve main body. Two ends of the slide valve seal the first and second air cylinders. The first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and the second air cylinder is connected to a last closed spiral flute through a second connection pipe. The slide valve searches for balance under the driving of pressures in the first and second air cylinders. The screw compressor having a slide valve with a flexible volume ratio can enable the volume ratio of the compressor to be automatically adjusted to an optimal state.

BACKGROUND OF THE PRESENT INVENTION

1. Field of Invention

The present invention relates to a screw compressor in the field of compressor technologies, and more particularly to a screw compressor having a slide valve with a flexible volume ratio.

2. Description of Related Arts

A twin-screw compressor is formed by a pair of male and female screws parallel to and engaged with each other, and is the most widely applied kind of compressor among rotary compressors.

An indicator diagram of a screw compressor in ideal working conditions is shown in FIG. 1, where a shaded part indicates power consumption during one cycle. However, when actual working conditions of the screw compressor are different from the ideal working conditions (especially, when a great difference exists), a pressure at a compression end does not match an exhaust pressure, which likely incurs over-compression (delay in opening results in excessive compression) or under-compression (opening prematurely results in insufficient compression). In the ideal working conditions, an optimal volume ratio of the screw compressor is achieved. As shown in FIG. 4, the volume ratio of the screw compressor is equal to V_(max)/V_(compression end).

Referring to FIG. 2, FIG. 2 is an indicator diagram of a screw compressor in the case of over-compression. In the case of over-compression, the screw compressor additionally consumes part of power. Besides, when the screw compressor is opened, since a pressure in a spiral flute of the screw compressor is higher that an outside pressure, the noise may be increased at the same time.

Referring to FIG. 3, FIG. 3 is an indicator diagram of a screw compressor in the case of under-compression. In the case of under-compression, the screw compressor also additionally consumes part of power. Besides, when the screw compressor is opened, since a pressure in a spiral flute of the screw compressor is lower that an outside pressure, air may enter the screw compressor from the outside, and the noise is also increased at the same time.

The screw compressors in the prior art all have the foregoing problems.

SUMMARY OF THE PRESENT INVENTION

A technical problem to be solved by the present invention is to provide a screw compressor having a slide valve with a flexible volume ratio, so that the volume ratio of the screw compressor may be automatically adjusted to an optimal state, and power consumption and noise are reduced.

In order to solve the technical problem, the present invention adopts the following technical solutions.

A screw compressor having a slide valve with a flexible volume ratio comprises a casing, a screw, an air entry, an air outlet, a slide valve, a first air cylinder and a second air cylinder.

The slide valve is disposed between the first air cylinder and the second air cylinder.

The slide valve comprises a slide valve main body, and two ends of the slide valve main body are respectively a first end surface and a second end surface; sectional areas of the first end surface, the second end surface and the slide valve main body are the same, and the first end surface and the second end surface seal the first air cylinder and the second air cylinder respectively.

The first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and in the first air cylinder, a pressure generated by the first end surface corresponds to an exhaust pressure. The second air cylinder is connected to a last closed spiral flute through a second connection pipe, and in the second air cylinder, a pressure generated by the second end surface corresponds to a pressure at a compression end of the compressor, that is, an average pressure in the last closed spiral flute before the compressor exhausts.

The slide valve searches for balance under the driving of pressures in the first air cylinder and the second air cylinder, so as to achieve an optimal volume ratio of the compressor.

If the pressure generated by the first end surface is greater than that generated by the second end surface, that is, the exhaust pressure is greater than the pressure at the compression end of the compressor, the slide valve moves towards the second air cylinder, so as to increase the pressure at the compression end of the compressor.

If the pressure generated by the first end surface is less than that generated by the second end surface, that is, the exhaust pressure is less than the pressure at the compression end of the compressor, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor.

An elastic mechanism is disposed in the second air cylinder. One end of the elastic mechanism is connected to the second air cylinder, and the other end is connected to the second end surface. The elastic mechanism ensures unloading and starting of the compressor.

A screw compressor having a slide valve with a flexible volume ratio comprises a casing, a screw, an air entry, an air outlet, a slide valve, a first air cylinder and a second air cylinder.

The slide valve is disposed between the first air cylinder and the second air cylinder.

The slide valve comprises a slide valve main body, and two ends of the slide valve main body are respectively a first end surface and a second end surface, wherein the first end surface and the second end surface seal the first air cylinder and the second air cylinder respectively.

The first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and the second air cylinder is connected to a last closed spiral flute through a second connection pipe.

The slide valve searches for balance under the driving of pressures in the first air cylinder and the second air cylinder.

As a preferred solution of the present invention, sectional areas of the first end surface, the second end surface and the slide valve main body are the same, or not the same, or different from one another.

As a preferred solution of the present invention, the first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and in the first air cylinder, a pressure generated by the first end surface is in direct proportion to an exhaust pressure; the second air cylinder is connected to a last closed spiral flute through a second connection pipe, and in the second air cylinder, a pressure generated by the second end surface is in direct proportion to a pressure at a compression end of the compressor, that is, in direct proportion to an average pressure in the last closed spiral flute before the compressor exhausts.

As a preferred solution of the present invention, if the pressure generated by the first end surface is greater than that generated by the second end surface, the slide valve moves towards the second air cylinder, so as to increase the pressure at the compression end of the compressor; if the pressure generated by the first end surface is less than that generated by the second end surface, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor.

As a preferred solution of the present invention, an elastic mechanism is disposed in the second air cylinder, wherein one end of the elastic mechanism is connected to the second air cylinder, and the other end is connected to the second end surface; the elastic mechanism ensures unloading and starting of the compressor.

As a preferred solution of the present invention, the slide valve is disposed on one side of the screw.

As a preferred solution of the present invention, the screw compressor is a twin-screw compressor or a tri-rotor screw compressor.

The beneficial effect of the present invention lies in that, the screw compressor having a slide valve with a flexible volume ratio provided by the present invention enables the volume ratio of the screw compressor to be automatically adjusted to an optimal state, and reduces power consumption and noise.

The slide valve disposed in the screw compressor may adjust the pressures of the first air cylinder and the second air cylinder according to the exhaust pressure and the pressure at the compression end of the compressor, so that the exhaust pressure matches the pressure at the compression end of the compressor. If the pressure generated by the first end surface is greater than that generated by the second end surface, the slide valve moves towards the second air cylinder, so as to increase the pressure at the compression end of the compressor; if the pressure generated by the first end surface is less than that generated by the second end surface, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor, thus ensuring that the screw compressor may automatically adjust the volume ratio of the compressor in any working conditions, and achieving the optimal volume ratio.

In addition, an elastic mechanism is disposed in the second air cylinder, enabling the slide valve to always be close to the first air cylinder (that is, an air suction end) before the screw compressor is started, so that the volume ratio is the lowest and the screw compressor can be easily started.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an indicator diagram of a screw compressor in ideal working conditions.

FIG. 2 is an indicator diagram of a screw compressor in the case of over-compression.

FIG. 3 is an indicator diagram of a screw compressor in the case of under-compression.

FIG. 4 is a schematic view of volume change in one cycle of the screw compressor.

FIG. 5 is a schematic structural view of a screw compressor.

MEANINGS OF THE NUMERALS

 1. Casing  2. Screw  3. Slide valve 31. First end surface 32. Second end surface 33. First connection pipe 34. Second connection pipe 35. Spring  4. First air cylinder  5. Second air cylinder  6. Air outlet

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention are described in detail in the following with reference to the accompanying drawings.

Embodiment 1

Referring to FIG. 5, the present invention discloses a screw compressor having a slide valve with a flexible volume ratio, which includes: a casing 1, a screw 2, an air entry, an air outlet 6, a slide valve 3, a first air cylinder 4, a second air cylinder 5, and the slide valve 3 is disposed between the first air cylinder 4 and the second air cylinder 5. In addition, the slide valve 3 may be disposed on one side of the screw 2.

In this embodiment, the screw compressor is a twin-screw compressor, and definitely, the present invention may also be used in a tri-screw compressor.

The slide valve 3 includes a slide valve main body 30, and two ends of the slide valve main body 30 are respectively a first end surface 31 and a second end surface 32. In this embodiment, a sectional area S1 of the first end surface 31, a sectional area S2 of the second end surface 32 and a sectional area S3 of the slide valve main body 30 are the same. The first end surface 31 and the second end surface 32 respectively seal the first air cylinder 4 and the second air cylinder 5.

The first air cylinder 4 is connected to the air outlet of the compressor through a first connection pipe 33, and in the first air cylinder 4, a pressure generated by the first end surface 31 corresponds to an exhaust pressure. The second air cylinder 5 is connected to a last closed spiral flute of the screw compressor through a second connection pipe 34, and in the second air cylinder 5, a pressure generated by the second end surface 32 corresponds to a pressure at a compression end of the compressor, that is, an average pressure in the last closed spiral flute before the compressor exhausts.

The slide valve 3 searches for balance under the driving of the first air cylinder 4 and the second air cylinder 5, so as to achieve an optimal volume ratio of the compressor. If the pressure generated by the first end surface 31 is greater than that generated by the second end surface 32, that is, the exhaust pressure is greater than the pressure at the compression end of the compressor, the slide valve 3 moves towards the second air cylinder 5, so as to increase the pressure at the compression end of the compressor. If the pressure generated by the first end surface 31 is less than that generated by the second end surface 32, that is, the exhaust pressure is less than the pressure at the compression end of the compressor, the slide valve 3 moves towards the first air cylinder 4, so as to decrease the pressure at the compression end of the compressor.

In addition, an elastic mechanism, spring 35, is disposed in the second air cylinder 5, where one end of the spring 35 is connected to the second air cylinder 5, and the other end is connected to the second end surface 32, so that the slide valve is always close to the first air cylinder (that is, an air suction end) before the screw compressor is started, and in this way the volume ratio is the lowest and the screw compressor can be easily started.

Embodiment 2

In this embodiment, the sectional area of a first end surface, the sectional area of a second end surface and the sectional area of a slide valve main body are the same, or not the same, or different from one another.

This embodiment provides a screw compressor having a slide valve with a flexible volume ratio, which includes a casing, a screw, an air entry, an air outlet, a slide valve, a first air cylinder and a second air cylinder. The slide valve is disposed between the first air cylinder and the second air cylinder. The slide valve includes the slide valve main body, and two ends of the slide valve main body are respectively the first end surface and the second end surface, where the first end surface and the second end surface seal the first air cylinder and the second air cylinder respectively. The first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and the second air cylinder is connected to a last closed spiral flute through a second connection pipe. The slide valve searches for balance under the driving of pressures in the first air cylinder and the second air cylinder.

Preferably, the first air cylinder is connected to the air outlet of the compressor through the first connection pipe, and in the first air cylinder, a pressure generated by the first end surface is in direct proportion to an exhaust pressure; the second air cylinder is connected to the last closed spiral flute through the second connection pipe, and in the second air cylinder, a pressure generated by the second end surface is in direct proportion to a pressure at a compression end of the compressor, that is, the pressure generated by the second end surface is in direct proportion to an average pressure in the last closed spiral flute before the compressor exhausts.

If the pressure generated by the first end surface is greater than that generated by the second end surface, the slide valve moves towards the second air cylinder, so as to increase the pressure at the compression end of the compressor; if the pressure generated by the first end surface is less than that generated by the second end surface, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor.

To sum up, the screw compressor having a slide valve with a flexible volume ratio provided by the present invention enables the volume ratio of the compressor to be automatically adjusted to an optimal state, thus reducing power consumption and noise.

The slide valve disposed in the screw compressor may adjust the pressures of the first air cylinder and the second air cylinder according to the exhaust pressure and the pressure at the compression end of the compressor, so that the exhaust pressure matches the pressure at the compression end of the compressor. If the pressure generated by the first end surface is greater than that generated by the second end surface, the slide valve moves towards the second air cylinder, so as to increase the pressure at the compression end of the compressor; if the pressure generated by the first end surface is less than that generated by the second end surface, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor, thus ensuring that the screw compressor may automatically adjust the volume ratio of the compressor in any working conditions, and achieving the optimal volume ratio.

In addition, an elastic mechanism is disposed in the second air cylinder, so that the slide valve is always close to the first air cylinder (that is, the air suction end) before the screw compressor is started, and in this way the volume ratio is the lowest and the screw compressor can be easily started.

The description and application of the present invention here are merely for exemplary purpose, and are not intended to limit the scope of the present to the above embodiments. The variations and modifications of the embodiments disclosed herein are possible, and for persons with ordinary skill in the art, the replacement of the embodiments and various equivalent parts are publicly known. It should be clear to persons skilled in the art that, the present invention may be implemented through other forms, structures, arrangements, proportions and other components, materials and parts without departing from the spirit and essential features of the present invention. Other deformations and variations may be made to the embodiments disclosed here without departing from the scope and spirit of the present invention. 

What is claimed is:
 1. A screw compressor having a slide valve with a flexible volume ratio, wherein the screw compressor comprises a casing, a screw, an air entry, an air outlet, a slide valve, a first air cylinder and a second air cylinder; the slide valve is disposed between the first air cylinder and the second air cylinder; the slide valve comprises a slide valve main body, and two ends of the slide valve main body are respectively a first end surface and a second end surface; sectional areas of the first end surface, the second end surface and the slide valve main body are the same, and the first end surface and the second end surface seal the first air cylinder and the second air cylinder respectively; the first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and in the first air cylinder, a pressure generated by the first end surface corresponds to an exhaust pressure; the second air cylinder is connected to a last closed spiral flute through a second connection pipe, and in the second air cylinder, a pressure generated by the second end surface corresponds to a pressure at a compression end of the compressor, that is, an average pressure in the last closed spiral flute before the compressor exhausts; the slide valve searches for balance under the driving of pressures in the first air cylinder and the second air cylinder, so as to achieve an optimal volume ratio of the compressor; if the pressure generated by the first end surface is greater than that generated by the second end surface, that is, the exhaust pressure is greater than the pressure at the compression end of the compressor, the slide valve moves towards the second air cylinder, so as to increase the pressure at the compression end of the compressor; if the pressure generated by the first end surface is less than that generated by the second end surface, that is, the exhaust pressure is less than the pressure at the compression end of the compressor, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor; and an elastic mechanism is disposed in the second air cylinder, wherein one end of the elastic mechanism is connected to the second air cylinder, and the other end is connected to the second end surface; the elastic mechanism ensures unloading and starting of the compressor.
 2. A screw compressor having a slide valve with a flexible volume ratio, wherein the screw compressor comprises a casing, a screw, an air entry, an air outlet, a slide valve, a first air cylinder and a second air cylinder; the slide valve is disposed between the first air cylinder and the second air cylinder; the slide valve comprises a slide valve main body, and two ends of the slide valve main body are respectively a first end surface and a second end surface; the first end surface and the second end surface respectively seal the first air cylinder and the second air cylinder; the first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and the second air cylinder is connected to a last closed spiral flute through a second connection pipe; and the slide valve searches for balance under the driving of pressures in the first air cylinder and the second air cylinder.
 3. The screw compressor having a slide valve with a flexible volume ratio as in claim 2, wherein, sectional areas of the first end surface, the second end surface and the slide valve main body are the same, or not the same, or different from one another.
 4. The screw compressor having a slide valve with a flexible volume ratio as in claim 2, wherein, the first air cylinder is connected to the air outlet of the compressor through the first connection pipe, and in the first air cylinder, a pressure generated by the first end surface is in direct proportion to an exhaust pressure; and the second air cylinder is connected to the last closed spiral flute through the second connection pipe, and in the second air cylinder, a pressure generated by the second end surface is in direct proportion to a pressure at a compression end of the compressor, that is, in direct proportion to an average pressure in the last closed spiral flute before the compressor exhausts.
 5. The screw compressor having a slide valve with a flexible volume ratio as in claim 2, wherein, if a pressure generated by the first end surface is greater than that generated by the second end surface, the slide valve moves towards the second air cylinder, so as to increase a pressure at a compression end of the compressor; and if the pressure generated by the first end surface is less than that generated by the second end surface, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor.
 6. The screw compressor having a slide valve with a flexible volume ratio as in claim 2, wherein, an elastic mechanism is disposed in the second air cylinder, one end of the elastic mechanism is connected to the second air cylinder, and the other end is connected to the second end surface; the elastic mechanism ensures unloading and starting of the compressor.
 7. The screw compressor having a slide valve with a flexible volume ratio as in claim 2, wherein, the slide valve is disposed on one side of the screw.
 8. The screw compressor having a slide valve with a flexible volume ratio as in claim 2, wherein, the screw compressor is a twin-screw compressor or a tri-rotor screw compressor. 